1. Field of the Invention
This invention relates to a vehicle headlamp comprising a leveling unit and a mechanical drive type beam switching device.
2. Description of the Related Art
Vehicle headlamps are designed to emit low or high beams via reflectors which reflect light from light source bulbs to a forward point. With respect to light sources (discharge light-emitting portions or filaments), though different light sources are generally used for low and high beams, respectively, because the direction of emitting the low beam differs from that of emitting the high beam, a vehicle headlamp using a single light source is also well known. Particularly in a two-lamp type vehicle headlamp using a discharge bulb as a light source bulb, a single light source arrangement is common.
In the case of a vehicle headlamp using such a single light source, a beam switching device switches a low beam to a high beam, and vice versa, by mechanically displacing optical elements such as the light source bulb, the reflector and the like.
In addition, a leveling unit is often provided in the vehicle headlamp for preventing a glare from bothering drivers of other vehicles. The leveling unit is arranged so that a low beam may be emitted in an optimum direction by vertically varying the direction in which the low beam is emitted, in accordance with a change in the posture of a vehicle body under control. In particular, the necessity of a leveling unit is greater when the vehicle headlamp is equipped with the discharge bulb that has a greater power than that of a halogen bulb or the like.
When the leveling unit is provided for the vehicle headlamp fitted with the beam switching device mentioned above, an actuator is necessary for each of the beam switching devices and leveling units.
In a vehicle headlamp of FIG. 10, for example, a beam-switching actuator 104 is required for longitudinally displacing a shade 102, and a leveling actuator 110 is required for vertically tilting a reflector 108 coupled to the leading end portion of an output rod 106 that has been displaced longitudinally. When two actuators are provided like this, a problem exists in that the lamp construction tends to be complicated, the weight is increased and the lamp becomes expensive.